/**
 * Local-storage draft persistence.
 *
 * Drafts are keyed by the form-filler's contact id so a single browser used
 * for multiple co-ops (rare but possible) keeps each draft separate.
 *
 * We persist values + a timestamp. On load, if a draft is younger than
 * MAX_DRAFT_AGE_MS, it overrides the server-side prefill. Otherwise it's
 * discarded (stale drafts probably represent abandoned sessions, and the
 * server-side prefill is fresher anyway).
 */

const MAX_DRAFT_AGE_MS = 1000 * 60 * 60 * 24 * 30; // 30 days

interface Draft {
  values: Record<string, unknown>;
  savedAt: string;
}

function key(cid: string): string {
  return `coop-checkin:draft:${cid}`;
}

export function loadDraft(cid: string): Draft | null {
  if (typeof window === "undefined") return null;
  try {
    const raw = window.localStorage.getItem(key(cid));
    if (!raw) return null;
    const parsed = JSON.parse(raw) as Draft;
    if (Date.now() - new Date(parsed.savedAt).getTime() > MAX_DRAFT_AGE_MS) {
      window.localStorage.removeItem(key(cid));
      return null;
    }
    return parsed;
  } catch {
    return null;
  }
}

export function saveDraft(cid: string, values: Record<string, unknown>): void {
  if (typeof window === "undefined") return;
  try {
    const draft: Draft = { values, savedAt: new Date().toISOString() };
    window.localStorage.setItem(key(cid), JSON.stringify(draft));
  } catch {
    // localStorage might be unavailable (private mode, quota). Silent ok.
  }
}

export function clearDraft(cid: string): void {
  if (typeof window === "undefined") return;
  try {
    window.localStorage.removeItem(key(cid));
  } catch {
    // ignore
  }
}